B737-900 crew at 11900 ft have an near midair collision with a BE35 at approximately 12000 ft VFR.

Attributes
ACN	563677
Time
Date	200210
Day	Thu
Local Time Of Day	0601 To 1200
Place
State Reference	NV
Altitude	msl bound lower : 11900 msl bound upper : 12000
Environment
Flight Conditions	Mixed
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : l30.tracon tower : cmh.tower
Operator	common carrier : air carrier
Make Model Name	B737-800
Operating Under FAR Part	Part 121
Navigation In Use	other
Flight Phase	descent : approach
Route In Use	arrival star : ns
Flight Plan	IFR
Aircraft 2
Controlling Facilities	tracon : l30.tracon
Operator	general aviation : personal
Make Model Name	Bonanza 35
Operating Under FAR Part	Part 91
Flight Phase	cruise : level
Flight Plan	VFR
Person 1
Affiliation	government : faa
Function	controller : approach
Qualification	controller : radar
Experience	controller radar : 14 controller time certified in position1 : 3
ASRS Report	563677
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Events
Anomaly	conflict : nmac conflict : airborne critical non adherence : far
Independent Detector	atc equipment : conflict alert atc equipment other atc equipment : radar/mode c aircraft equipment : tcas other controllera other flight crewa other flight crewb
Resolutory Action	controller : issued advisory flight crew : took evasive action other
Consequence	faa : investigated
Miss Distance	horizontal : 0 vertical : 0
Supplementary
Problem Areas	Flight Crew Human Performance ATC Human Performance
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

VFR aircraft maintaining VFR on top of a layer climbed to a non VFR altitude. Air carrier X was 100 ft below assigned altitude. Traffic exchanged. TCASII told air carrier X to climb. Radar displayed no separation from targets. Prior to event, traffic was called and VFR aircraft was asked to maintain a VFR altitude if possible.

Original NASA ASRS Text

Title: B737-900 CREW AT 11900 FT HAVE AN NMAC WITH A BE35 AT APPROX 12000 FT VFR.

Narrative: VFR ACFT MAINTAINING VFR ON TOP OF A LAYER CLBED TO A NON VFR ALT. ACR X WAS 100 FT BELOW ASSIGNED ALT. TFC EXCHANGED. TCASII TOLD ACR X TO CLB. RADAR DISPLAYED NO SEPARATION FROM TARGETS. PRIOR TO EVENT, TFC WAS CALLED AND VFR ACFT WAS ASKED TO MAINTAIN A VFR ALT IF POSSIBLE.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.